Shield tunneling in gravel stratum is often faced with many difficulties such as large torque of cutterhead,tool wear,and poor slag.Aiming at the research problem of reasonable conditioning index of gravel soil,the typical gravel soil layer of Qingdao Metro Line 4 is taken as the research object.Firstly,the basic characteristics of gravel soil are evaluated by particle screening,LCPC test,and permeability test.Five groups of gravel soil conditioning schemes were designed based on the traditional conditioning schemes of sand and clay soil.Slump test,permeability test,and direct shear test were carried out to analyze the flow plasticity,permeability and shear resistance characteristics of gravel soil with different conditioning indices.Finally,the best scheme of foam and polymer combin-ation conditioning was verified according to the variation of torque of the shield machine in practical engineering.The results show that the mixture of 7%foam and 5%polymer can effectively reduce the permeability coefficient of gravel soil,maintain certain plasticity,and play a role in reducing the torque of the cutterhead and improving tunneling efficiency.
关键词
地铁/土压平衡盾构/碎石土/坍落度/渗透性/直剪试验
Key words
subway/earth pressure balance shield/gravel soil/slump test/permeability/direct shear test
维普
万方数据